1. Field of the Invention
The present invention is generally in the field of semiconductors. More specifically, the present invention is in the field of fabrication of power semiconductor devices.
2. Background Art
Power semiconductor devices, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), for example, are widely used in a variety of electronic devices and systems. Examples of such electronic devices and systems are power supplies and motor controllers, in which vertically conducting trench type silicon MOSFETs, for instance, may be implemented as power switches.
As the performance requirements placed on modern electronic systems grow ever more stringent, power losses within a semiconductor device, as well as factors affecting switching speed, become increasingly important. One measure of the efficiency of a power MOSFET switch is its ON-resistance, or Rdson. Optimizing Rdson in a vertical trench MOSFET, for example, may require carefully controlling the length of the channel. That is to say, implementation of a vertical trench MOSFET having a short channel may improve the Rdson characteristic of the device.
However, attempts to lower Rdson by reducing channel length may give rise to significantly undesirable operational phenomena as byproducts of the constraints imposed during the fabrication process. For example, current leakage when the MOSFET is in a nominally OFF state may sometimes be observed in short channel vertical devices otherwise displaying highly desirable performance characteristics. Unfortunately, conventional power semiconductor fabrication strategies have failed to achieve optimum performance while also adequately assuring device reliability by preventing current leakage when the device is switched OFF.
Thus, there is a need to overcome the drawbacks and deficiencies in the art by providing a semiconductor device configured to prevent current leakage during an OFF state of the device.